In the upcoming year of this grant we will continue our investigation of the immunologic characteristics of human colostral lymphocytes and the in vivo characteristics of rat mammary gland T lymphocytes. Studies will be centered in two areas: (1) assessment of the regulatory processes controlling alloreactivity in human colostrum. These studies will concentrate on maternal reactivity toward paternal HLA antigens expressed on neonatal target cells; (2) utilizing a rat model to delineate the cellular basis of cell-mediated immunity in the lactating mammary gland, we have recently determined, using standard radioisotopic labelling and adoptive transfer techniques, that T lymphocytes destined for the mammary gland are derived from a variety of host tissues. Experiments in the upcoming year will probe the specificity and control of this lymphocyte migration.